In the case of Pettibone v. United States in 1892, the Supreme Court ruled that a person cannot be charged with obstructing justice if they were not aware that a federal investigation was underway at the time of their actions. The case involved defendants who had been convicted for conspiring to prevent testimony in a federal court by kidnapping potential witnesses. However, when these acts were committed, there was no ongoing proceeding before any commissioner or court of the United States and thus it could not have been known by them that such proceedings would take place later on. Therefore, according to Justice David Brewer's majority opinion, since they did not know about any impending legal action at the time they conspired to kidnap potential witnesses; their actions did not constitute obstruction of justice under existing law.

In the dissenting opinion for Pettibone v. United States, Justice Brown argued that the majority's interpretation of conspiracy was too narrow and failed to consider broader implications. He contended that a group conspiring to obstruct justice by using force or threats should be held accountable even if their plan did not directly involve bribes or corruption. According to him, any act intending to impede judicial proceedings constitutes an obstruction of justice regardless of its nature or means used. Furthermore, he disagreed with the majority's view on jurisdictional issues; he believed federal courts had authority over such cases because they involved interference with federal functions and officers - in this case, a U.S Marshal executing court orders during labor disputes in Idaho territory.